7 replies to this topic

[Susuwatari]

I'd like to try making a multicart that can handle 8K games. F8 bankswitching scheme seems to be common so...

Would it be like building a regulat F8 cart plus switches for the higher addresses line to select the entire 8K blocks? Also any EPROM schematic diagram for the F8 cart? I'll figure the address switching if the schematic is for single 8K cart.

Finally where may I find a list of known 2600 carts that uses F8 bankswitching scheme?

[DanBoris]

This document by Kevin Horton:

http://www.tripoint....files/sizes.txt

Has a list of all the 2600 carts and what bankswitching shemes they used.

Building it shouldn't be to hard. The first 12 address lines on the ROM would be connected to the address lines from the processor, the 13th line would be the bankselect line, and the address lines above that would be to select the game.

Dan

[Susuwatari]

That list does help me looking up for the right game images. Too bad Parker Bros didn't use F8 scheme, there's quite a few PB games I don't have thqat I'd like to play on the real 2600.

I'll need an explaination how to handle the bankswitching. I'm guessing a few AND gates to watch address lines and toggle A13 on the ROM chip. I do know I'll have 5 hex inverter to spare since I need one to flip A1 for EPROM and hex inverter normally are 6 to a chip.

Quote

-F8: This is the 'standard' method to implement 8K carts.  There are two addresses which select between two unique 4K sections.  They are 1FF8 and 1FF9.  Any access to either one of these locations switches banks. Accessing 1FF8 switches in the first 4K, and accessing 1FF9 switches in the last 4K.  Note that you can only access one 4K at a time!

[Susuwatari]

Google is my friend

I should have checked Google before asking here.

                       |      

          -------------| >()--------------  Eprom

         |             |/                   Enable

         |                       5v  5v

    A12 -+-|-                   __|___|_

    A11 ---|                  | Set Rst|

    A10 ---|                  |        |

     A9 ---| 7            A0--|D  7   Q|-- A12

     A8 ---| 4 N              |   4    | of eprom

     A7 ---| 1 A |     |      |   7    |

     A6 ---| 3 N |()-+-| >()---|>  4    |

     A5 ---| 3 D |   | |/      |________|

     A4 ---|     /   |           

     A3 ---|    /   ___         

    /A2 ---|   /    ___ 1000pf (0.001 uf)

    /A1 ---|  /      |

        --|_/       |

                    gnd

That is just for A12 of the EPROM. A0 to A11 and all data lines are wired straight through (ie no change to the PCB board) and A12 is inverted via hex inverter to EPROM enable on the EPROM (pin 20 or 22 depending on the EPROM itself).

All extra A lines on EPROM are connected to the switch for selecting 8K bank. When I get a 74133 13 input NAND gate, I'm going to have some fun. Maybe I should pick up a dozen while I have the chance.

If I can find a 27c080 at a decent price, I could burn up to 128 games that uses F8 bankswitch and no extra hardware (Stargate/Defender 2 uses RAM and Pitfall 2 uses extra sound so both won't work) and that's pretty much all of the available F8 games with room for about 20 more. For now I'll have to contend with getting 120+ used 27c010 for under $25.

FWIW there are 16Mbit and 32Mbit EPROM, which would mean every 2600 games ever created could fit on one chip but it'd require some fancy ROM interleaving with confusing switching array from 2K to 16K and multitude of switches to enable proper bankswitching circuit and enable variety of SRAM support. I think a single PCB dedicated to specific bankswitch is far easier.

[jsoper]

My page (link below) has F8, F16, and Parker Brothers bankswitch stuff. Gotta add Tigervision
one of these days (never enough time).

[Susuwatari]

Funny that is exactly where I got the F8 diagram. So you know your site shows up in Google.

Also I see F6 on your site but I don't see F16 so I'm guessing a typo? From the look, I guess F6 diagram is compatible with F8 diagram meaning I could just build an F6 based EPROM cart and have 8K (doubled to 16K) and 16K on the same EPROM. Is that right? There are also 32K and 64K based that are similiar to F8 and F6 but only one game for 32K and 64K so I probably won't even try.

That PB diagram looks very complicated! I wouldn't be surprised if Tigervision used similiarly difficult setup. But I'll bet nothing compares to M-Nertwork scheme (E7) I took my Burgertime apart once and the whole thing was filled with several big chips.

[jsoper]

Susuwatari said:

Also I see F6 on your site but I don't see F16 so I'm guessing a typo?  From the look, I guess F6 diagram is compatible with F8 diagram meaning I could just build an F6 based EPROM cart and have 8K (doubled to 16K) and 16K on the same EPROM.  Is that right?  

That PB diagram looks very complicated!  I wouldn't be surprised if Tigervision used similiarly difficult setup.

Kinda a typo, I always think "16" for 16k, but Kevin Horton discusses it as F6.
Yeah, but you don't really wanna mix 16k and 8k. Making just an 8k multicart is a great fit
because a 27C080 can hold 128 8k games and that's just about how many there are (discounting hacks).
Tigervision is pretty simple, and PB isn't that bad (most of it came from Kevin Horton).
That was a fun one to finish because of all the negative comments I got
from AAers when starting the project:
"Don't hold your breath"
"Study emulator code"
"Parker Bros needed 5 chips"
"I said 'Study emulator code'"

[CPUWIZ]

jsoper said:

That was a fun one to finish because of all the negative comments I got
from AAers when starting the project:
"Don't hold your breath"
"Study emulator code"
"Parker Bros needed 5 chips"  
"I said 'Study emulator code'"